Microwave means



July 1962 o. c. LUN D$TROM ET AL 3,042,886

MICROWAVE MEANS Filed July 3, 1959 llnited fitates i atent antasst Patented July 3, 1962 its Ware

Filed July 3, 1959, Ser. No. 824,746 2 Ciaiins. (Cl. 333-98) The present invention relates to microwave transmission means and more particularly to means for coupling and/ or uncoupling a coaxial transmission line to a waveguide so as to control the flow of microwave power therepast.

It is very frequently desirable in microwave systems to couple a coaxial transmission line and a waveguide structure together for transmitting microwave power therebetween. Not infrequently such systems are subject to transient conditions wherein the power fluctuates over a sufiicient range to permanently damage one or more elements in the system. For example, a crystal diode placed in the wave section to act as a rectifier or modulator may break down if subjected to excessive amounts of power. In order to prevent such damage it has been proposed to disconnect the load from the power source during the transient conditions. Heretofore this has been accomplished by means of various shutter mechanisms located in the waveguide structure and/or coaxial cable so as to be efiective to prevent the transmission of power. When the transient condition has subsided the shutter is removed to permit the power to how therepast. If this action is automatically or remotely controlled it has normally been accomplished by means of a solenoid or similar means that moves the shutter mechanism. Such arrangements are cumbersome and unreliable in operation and also require considerable amounts of power to operate. In addition, these shutter structures have necessitated inserting some physical structure into the waveguide and also removing it therefrom. This in turn necessitates a sufiicient amount of discontinuity in the transmission system to create standing waves that interfere with the normal transmission of power therepast.

It is therefore an object of the present invention to provide a simple and high speed means for controlling the coupling and uncoupling of microwave power from one transmission path to another transmission path.

It is a further object of the present invention to provide means for coupling and uncoupling microwave power from one portion of transmission system to another portion of the system without producing any irregularities or discontinuities that will interfere with the noranal transmission of power therepast by producing standing waves in the system.

The foregoing objects are to be accomplished by an axially slidable coupling probe in a right angle junction between a coaxial transmission line and a waveguide. In the present instance the probe comprises a cylinder of a suitable dielectric material that is mounted in a housing on the waveguide for axial movement toward and away from the coaxial line. More particularly the probe is disposed transversely of the waveguide in axial alignment with the coaxial line so that the center conductor in the probe can be moved into or out of electrical contact with the center conductor of the coaxial line. When the conductors in the probe and coaxial line are not in contact there will be no coupling between the coaxial line and waveguide. However, when the conductors are in contact the conductor in the probe will be disposed in a radiating position in the waveguide structure so that the waveguide and coaxial line will be coupled.

It may thus be seen that whenever it is desirable to couple energy from the coaxial line into the waveguide the probe may be moved against the center core of the coaxial line. The center conductor in the probe will then be in intimate electrical contact with the center conductor of the coaxial line and will also be disposed in a radiating position inside of the waveguide. Thus the current in the center conductor of the coaxial line will flow into the center conductor of the probe and the microwave energy will be radiated into the waveguide for further transmission to the load. When it is desirable for the coaxial transmission line to be uncoupled from the waveguide the probe'is moved axially so as to disconnect the conductor in the probe from the center conductor in thecoaxial line. As a result of the space between the conductors, current will be unable to flow into the probe and no energy will be radiated into the waveguide.

In the drawing:

FIG. 1 is a perspective view of a coaxial transmission line and a waveguide structure that are coupled together by means embodying the present invention;

FIG. 2 is a cross-sectional view of the coupling means in FIG. 1;

FIG. 3 is a view similar to FIG. 1 but showing the coupling means disposed in another operating position; and

FIG. 4 is a cross-sectional view taken substantially along the plane of line 4-4 in FIG. 2.

Referring to the drawings in more detail the present invention is particularly adapted to be embodied in a junction 10 between a coaxial transmission line 12 and a waveguide structure 14 so as to control the coupling of microwave energy therebetween.

In the present instance the waveguide 14 is a rectangular structure having a pair of parallel broad walls 16 and 18 and a pair of parallel narrow walls 20 and 22 arranged to carry microwave energy therealong. One end of the waveguide 14 is terminated by an end wall 24 While the other end is open so as to permit the microwave energy to pass therefrom or thereinto.

A pair of aligned substantially cylindrical projections 26 and 28 extend outward from the broad walls 16 and 18 at substantially right angles thereto. The first projection 26 includes a passage 30 that extends axially therethrough so as to open into the interior of the waveguide 14. The outer end 32 of the passage 36 is enlarged and threaded so as to receive the terminal end of the coaxial transmission line 12. The outer conductor 34 of the line 12 will thus be electrically connected to the waveguide 14. The terminal end of the inner conductor 36 will be disposed adjacent the inner end of the enlarged portion 32. As a result of the inner conductor 36 not entering into the interior of the waveguide 14, the inner conductor 36 will be incapable of radiating any material amount of energy into the waveguide 14. Accordingly, microwave energy in the coaxial line 12 will not be coupled into the waveguide 14.

In order to permit coupling of the coaxial line 12 to the waveguide 14 a cylinder probe 38 of a suitable dielectric material such as Tefion is provided. The exterior of the probe is preferably a sliding fit in the passage 30 and a passage 40 in the projection 23. The probe 38 is preferably sufliciently long to permit the inner end 42 to engage the terminal end of the coaxial line 12 while the opposite end 44 thereof projects from the end of the passage 40. An enlarged head 46 may be provided on spaasse this end to prevent the probe 38 passing through the passage 48 when there is no coaxial line in the end 32 of the passage 36. p 7

The interior of the probe 38 includes a center conductor 48. One end of the conductor 48 projects just enough to engage the terminal end of the center conductor 36 of the coaxial line 12 when the probe 38 is disposed at its inner position (see FIG. 2). The other end of the conductor 48 preferably terminates near the center of the interior of the waveguide 14 when the probe 38 is in its inner position. Thus the conductor 48 will project about a quarter wavelength into the waveguide 14 and will be effective to radiate energy into the waveguide 14 so that the coaxial line 12 will be coupled to the waveguide 14. V

The probe 38 is freely slidable to an outer positron wherein the inner end 42 of the probe 38 will be spaced from the terminal end of the coaxial line 12 a sufficient distance to prevent any material amount of energy being coupled thereinto (see FIG. 3). As a result the coaxial transmission line 12 will be uncoupled and the micro wave energy in the coaxial line 12 will be unable to reach the load in the waveguide 14.

Any suitable means may be provided for controlling the position of the probe 38 and thus the amount of coupling between the coaxial line. 12 and waveguide 14. In the present instance it has been found advantageous to employ a spring 58 for biasing the probe 38 into one extreme position and a detent means 52 for retaining it in the other extreme position.

The spring 50 is mounted on a bracket 54 projecting from the waveguide 14 so that one end will seat on the enlarged head 46 on the end of the probe 38. Thus the spring 50 will depress the probe 38 and force it inwardly through the'passages 30 and 40 so as to be efiective to bias the probe 38 forcibly against the terminal end of 'any coaxial transmission line 12 secured in the enlarged end 32 of the passage 30. In the event there is no transmission line secured in position, the spring 50 will force the enlarged head 46 against the end of the projection 28 and retain the probe 38 in the passages 30 and 40.

The detent means 52 which is effective to retain the probe 38 in the other extreme or disengaged position includes a pin 56 that is slidably mounted in a passage 58 through the bracket 54 so that the inner end 64) thereof can slide across the end of the projection 28 and into a pocket 62 in the side of the probe 38. The pocket 62 is positioned so that it will only receive the end'6t of the pin 56 when the probe 38 is retracted and the ends of the conductors 36 and 48 are separated. The outer end of the pin 56 is attached to a lever 66 mounted on the waveguide 14 by means of a hinge 68. It is desirable to provide a sufficient amount of lost motion in this attachment to permit the lever 66 to swing about the axis of the hinge 68 without causing any binding of the pin 56. When the lever 66 is positioned adjacent the end wall 24 of the waveguide 14 the pin 56 can extend into the pocket 62 and retain the probe 38 in the retracted position. However, when the lever 66 is rotated about the axis of the hinge 68 and away from the end wall 24 the end of the pin 56 Will be pulled out of the pocket 62. The probe 38 will then be free to move through the passages 39 and 40 and the spring 50 will force the probe 38 to slide against the terminal end of the line 12 so that the ends of the conductors 36 and 48 will be in electrical contact.

. The lever 66 may be controlled by any suitable means such as an electrically ignited squib 70. Such a squib is very light and reliable in operation and requires a very small amount of power to actuate it. The squib 70 is preferably located between the end wall 24 and the lever 66. When the squib 7 is ignited it will explode and force the lever 66 to swing outwardly about the axis of the hinge 68. As the lever 66 swings it will pull the end 60 of the pin 56 out of the pocket 62. This in turn will release the probe 38 and allow the spring 50 to force the probe 38'to rapidly slide through the passages 39 and 40 and engage the terminal end' of the line 12. Accordingly, the conductors 36 and 48 will be in electrical contact and since the conductor 48 is now disposed across the waveguide 14 the coaxial transmission line 12 and the waveguide 14 will be coupled together.

It may thus be seen that means have been provided for controlling the flow of microwave power in a system having a' source of energy feeding into a coaxial transmission line 12 and a load absorbing energy from a waveguide structure 14. When the energy or power level in the'system is subject to excessive fluctuations, for example, during transient conditions, the probe 38 can be pulled into the retracted position and the pin 56 forced into the pocket 62. This will maintain the center conductors 36 and 48 in the transmission line 12 and in the probe 38 widely separated. As a result there will be no current in the conductor 48 and no energy can be coupled into the waveguide 14. Thus even though the power in the transmission line 12 temporarily rises to excessively high levels the power will not be coupled into the waveguide 14 and the load will be protected from absorbing destructive amounts of power. After the transient conditions are terminated and the power level has stabilized, the squib 78 may be fired. The resultant explosion will cause the lever 66 to swing about the axis of the hinge 68 and extract the pin 56 from the pocket 62 in the probe 33. This in turn will release the probe 38 and permit the spring 59 to force the probe 38 to rapidly slide inwardly through the passages 38 and 48 and against the terminal end of the coaxial line 12. This will enable current to flow in the center conductor 48 so as to couple line 12 to the waveguide 14. It may thus be seen that the microwave energy will flow from the conductor 36 in the transmission line 12 into the conductor 48 in the probe 38 and thus be coupled into the waveguide '14 without producing an undesirable amount of standing waves.

What is claimed is:

1. A microwave switching device comprising a rectangular waveguiding structure having first and second broad sides and first and second narrow sides, said first and second broad sides having first and second apertures, respectively, centrally disposed opposite each other intermediate said first and second narrow sides; a coaxial line having an inner conductor and an outer conductor disposed normal to said first broad side of said waveguiding structure, said outer conductor being electrically connected to said first broad side thereof about said first aperture and said inner conductor terminating at a point exterior to the volume defined by said first and second broad and narrow sides;

. an elongated dielectric member disposed through said second aperture transversely to said wave-guiding structure; means for maintaining said elongated member in first and second stable positions, said first position being immediately adjacent the inner extremity of said coaxial line and said second position being spacedtherefrom; and an elongated conductive element disposed longitudinally within said elongated dielectric member in alignment with said inner conductor of said coaxial line, said elongated conductive element having the extremity thereof nearest said coaxial line exposed and the remaining extremity thereof within said elongated dielectric member protruding into the volume defined by said first and second broad and narrow sides of said waveguiding structure thereby to couple said coaxial line to said waveguiding structure when said elongated dielectric member is in said first stable position.

2. The microwave switching device as defined in claim 1 which additionally includes means for maintaining a spring biasing force on said elongated dielectric member for moving said member from said second stable position to said first stable position, and explosive means for releasing said dielectric member from said second stable 2,668,276 Schooley Feb. 2, 1954 6 Rustad May 29, 1956 Zaleski Mar. 26, 1957 Braden Dec. 10, 1957 Berko'witz July 28, 1959 OTHER REFERENCES Bollinger: Abstract of application Serial No. 694,044, published Nov. 21, 1950, 640 O.G. 1040. 

